Black antifouling coating compositions

ABSTRACT

A method for preventing the growth of white calcareous deposits on black antifouling coated surfaces of marine vessels which are protected from corrosion by sacrificial metal anodes by applying to the surface a coating containing black iron oxide and copper compounds.

United States Patent 1nventor John D. White Little Falls, NJ.

Appl. No. 827,887

Filed May 26, 1969 Patented Nov. 16, 1971 Assignee Celanese CoatingsCompany New York, N.Y.

BLACK ANTIFOULING COATING [56] References Cited UNITED STATES PATENTS3,010,886 1 H1961 Chappell 204/149 3,497,434 2/1970 Littauer 204/1963,505,758 4/1970 Willisford 1 14/222 OTHER REFERENCES J. of PaintTechnology," Vol.41, 1969, pp. 285- 303 Primary Examiner-Ta-Hsung TungAttorneys-T. .1. Morgan, L. l. Grim and H. P. Price ABSTRACT: A methodfor preventing the growth of white calcareous deposits on blackantifouling coated surfaces of marine vessels which are protected fromcorrosion by sacrificial metal anodes by applying to the surface acoating containing black iron oxide and copper compounds.

is particularly 1 BLACK ANTIFOULING COATING COMPOSITIONS BACKGROUND OFTIIE INVENTION The field to which this invention is directed is tocoating compositions which contain an antifouling agent.

The problem of protecting the underwater surfaces of marine structuresfrom the action and attachment of marine fouling organisms has been aserious and long existing one. A number of different types of coatingcompositions have been used to solve this problem with varying degreesof success. Coatings of this type are described in 41 Journal of PaintTechnology 285 (1969) in an article entitled Marine Biology inAntifouling Paints."

The color of the surfaces of ships protected by antifouling paints isgenerally not a problem since such surfaces are below the waterline anddo not have much of an effect upon the overall aesthetic appearance.However, in a camouflage system that color of the coating becomes veryimportant. This so in the painting of submarines.

White or light-colored calcareous deposits will form on the surfaces ofsteel hulls in sea water which are protected from corrosion withsacrificial metal anodes and are coated with conventional blackantifouling paints. Such calcareous deposits are various insolublecompounds of calcium and magnesium. These deposits will also form onmetal anode-protected bare steel immersed in sea water but do notnormally form on painted steel or steel protected with antifoulingpaints which are not black in color.

The formation of the white calcareous deposits on the black antifoulingpainted surface is a serious problem for two reasons. First, foulingorganisms can grow on the calcareous deposits thus negating theeffectiveness of the antifouling paint. Secondly, the white deposits onthe black background upsets camouflage designs, particularly onsubmarines.

SUMMARY OF THE INVENTION This invention pertains to black pigmentedantifouling paints and in particular to black-colored antifouling paintswhich are suitable for use as camouflage paints on submarines. Inanother aspect this invention is directed to a process for preventingthe growth of white calcareous deposits on black antiflowing paintedsteel surfaces, protected from corrosion by sacrificial metal anodes andimmersed in sea water.

DESCRIPTION OF THE INVENTION The black antifouling paints used in thisinvention contain black iron oxide as the only black pigment and copperor copper compounds as the antifouling components.

The copper antifouling pigment used in this invention is finely dividedcopper or copper-containing components. Cuprous oxide is preferredbecause of its high toxicity and antifouling effectiveness. The cuprousoxide can be any conventionally known type, anhydrous or hydrated, andtypes such as pyrometallurgical and electrolytic process cuprous oxide.Mixtures of copper is various forms can also be used, particularlymixtures of finely divided copper and couprous oxide.

Small amounts, up to about 3 weight percent of the total film-formingcomposition, of other toxic pigments can be used in admixture with thecopper antifouling pigment without departing from the spirit of theinvention. Examples of such pigments include tributyltin fluoride,mercuric oxide, arsenic oxide, bis(tri-n-butyltin) oxide, phenarsazinechloride and the like.

The black iron oxide utilized in this invention includes both thenatural black iron oxide and the synthetic black iron oxide. Naturalblack iron oxide is made from magnetite ore which is ground dry andclassified to produce the pigment which has a range of particles sizesfrom about I to 4 microns. The pigment contains at least about 94percent by weight of H2 with minor amounts of SiO, and M 0 Precipitatedblack iron oxide is made by the reaction of a ferrous salt and analkali, followed by oxidation. The precipitate is washed untilsalt-free, filtered, dried and powdered. This pigment usually containsat least about 98 percent weight iron oxides, with the remainder beingwater, silica, calcium carbonate and alumina. Particle sizes range fromabout 0.1 to 1.5 microns.

The matrix which can be used in this invention is either the insolubleor soluble matrix type. The insoluble matrix type antifouling coatingcontains pigments and, as the vehicle, an organic film-forming resinwhich does not dissolve in sea water. The toxic pigment is released bycontinuous contact of toxic particles or by diffusion through the paint.Vehicles of this type include vinyl resins (vinyl chloride-vinyl acetatecopolymers), chlorinated synthetic rubber, butyl rubber, phenolic-basevarnishes and the like.

The soluble matrix type coatings are those in which the toxic and thevehicle are removed by dissolution of the vehicle, mechanical erosion ofthe vehicle and bacterial or biodegradable action on the vehicle. Theprime ingredient in such a vehicle is rosin which will slowly dissolvein alkaline sea water. Other soluble vehicles are hydrogenated rosin andabietic acid. Mixtures of soluble and insoluble matrices can also beused as well as small amounts of natural and synthetic resinouscompositions. Matrices used in antifouling paints are described in 41Journal of Paint Technology 285 (1969).

In preparing the coating compositions of this invention the coppercompound and the black iron oxide are blended with the organic vehicleby any suitable means, such as by milling or with high-speed mixing.Suflicient solvents, such as ketones, alcohols, esters and hydrocarbons,are added to obtain application viscosities. Generally, such solventswill be about 10 to 25 weight percent of the total composition. Smallamounts of clays and other suspending agents can be used as well asplasticizers and the like.

The amount of copper compound used in this invention is about 50 toabout 75 weight percent based on total solids (dry coating). The amountof black iron oxide is about 10 to about 25 weight percent, again basedon total solids. The organic matrix is used in amount sufficient to forma continuous coating with tee pigments and is generally present inamounts of about 5 to 25 weight percent.

Although the antifouling coatings hereinbefore described can be used onany marine type structures, they are particularly adaptable for use onmetal hulls which are protected from corrosion by cathodic protection.This method involves either the use of a sacrificial anode whichcorrodes preferentially and thus protects the coated surface by makingit the cathode, or impressing, from an external source, a'direct currentcounter to the natural corrosion current. The principles of galvaniccorrosion are put to advantageous use. Sacrificial anodes are made fromzinc, magnesium, and aluminum with zinc being preferred.

The following examples describe the invention in more detail. Partswhere used are parts by weight.

EXAMPLE 1 A black antifouling coating composition was made from 59.03parts cuprous oxide pigment, 10.18 parts of black iron oxide containinga minimum of 98 percent iron oxides, 2.34 parts vinyl resin, 9.62 partsrosin, 2.08 parts tricresyl phosphate, 0.36 part clay-suspending agent,10.1 parts methyl isobutyl ketone, 6.17 parts xylene, and 0.12 partmethanol.

EXAMPLE 2 A coating similar to example 1 was prepared using 59.03 partsof copper pigments which were a mixture of cuprous oxide and copper(90.6 percent cuprous oxide and 5.6 percent copper), in place of thecuprous oxide as used in example 1 EXAMPLE 3 This coating compositionwas made using lampblack in place of the black iron oxide. Thecomponents were: 63.16 parts cuprous oxide, 3.89 parts lampblack, 2.50parts vinyl resin, 10.29 parts rosin, 2.23 parts tricresyl phosphate,0.39

parts clay-suspending agent, 0.81 parts methyl isobutyl ketone, 6.6parts xylene and 0.13 parts methanol.

EXAMPLE 4 This coating composition was made using the formula of example3 but replacing the cuprous oxide with 59.03 parts of the copper pigmentused in example 2.

One side of steel panels were coated with each of the compositionsdescribed in example l through 4. After the coatings were thoroughlydried, a large section of a zinc anode was attached to the unpaintedside of each panel. The panels were then immersed in sea water for oneweek. White calcareous deposits formed on the black surfaces of thepanels coated with the compositions of examples 3 and 4. No depositsformed on the panels coated with the composition of example 1 and 2.

it is to be understood that the foregoing detailed description is givenmerely by way of illustration and that many variations may be madetherein without departing from the spirit of the invention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

I claim:

l. A marine vessel, the steel hull of which is protected from corrosionby sacrificial metal anodes, the exterior of said hull being coated withan antifouling black camouflage paint which contains a black pigment andan antifouling ingredient,

wherein said black pigment consists essentially of black iron oxide andsaid antifouling ingredient consists essentially of copper, coppercompounds, or mixtures thereof.

2. The vessel of claim I wherein the antifouling ingredient is cuprousoxide.

3. The vessel of claim 1 wherein the paint contains about 50 to about 75weight percent copper pigment and about 10 to about 25 weight percentblack iron oxide, said weight percents being based on the total weightof dry coating.

4. The vessel of claim 1 wherein the sacrificial metal anode lS ZlnC.

5. A process for preventing the formation of white calcareous depositson black camouflaged painted exterior surfaces of submarines, saidsurfaces being protected from corrosion by sacrificial metal anodeswhich comprises applying to the exterior surface a black antifoulingpaint which contains only black iron oxide as the black pigment andcopper, copper compounds or mixtures thereof as the antifoulingingredient.

6. The process of claim 5 wherein the antifouling ingredient is cuprousoxide.

7. The process of claim 5 wherein the paint contains about 50 to about75 weight percent copper pigment and about 10 to about 25 weight percentblack iron oxide, said weight percents being based on the total weightof dry coating.

8. The process of claim 5 wherein the sacrificial metal anode is zinc.

UMTED STATES PATENT QFFICE CEREEFEQATE OF CORREUEEGN Patent No.3,620,943 Dated November 16, 1971 Inventor g John D.

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

In column 1, line 57, delete "is" and insert -in-; line 58 I delete"couprous" and insert -cuprou s--; line 70, delete "4" and insert 40--.

In column 2, line 39, delete "tee" and insert --the--.

In column 3, line 1, delete "0.81" and insert --l0.8l--.

Signed and sealed this 23rd day of May 1972.

SEAL} attest:

IDWARD M.FLETCEER, JR. ROBERT GOTTSCHALK tttesting Officer Com issionerof. Patents

2. The vessel of claim 1 wherein the antifouling ingredient is cuprous oxide.
 3. The vessel of claim 1 wherein the paint contains about 50 to about 75 weight percent copper pigment and about 10 to about 25 weight percent black iron oxide, said weight percents being based on the total weight of dry coating.
 4. The vessel of claim 1 wherein the sacrificial metal anode is zinc.
 5. A process for preventing the formation of white calcareous deposits on black camouflaged painted exterior surfaces of submarines, said surfaces being protected from corrosion by sacrificial metal anodes which comprises applying to the exterior surface a black antifouling paint which contains only black iron oxide as the black pigment and copper, copper compounds or mixtures thereof as the antifouling ingredient.
 6. The process of claim 5 wherein the antifouling ingredient is cuprous oxide.
 7. The process of claim 5 wherein the paint contains about 50 to about 75 weight percent copper pigment and about 10 to about 25 weight percent black iron oxide, said weight percents being based on the total weight of dry coating.
 8. The process of claim 5 wherein the sacrificial metal anode is zinc. 